The present invention concerns a pilot valve. The pilot valve controls the pneumatically actuated main valve of a milking-system pulsator. An electromagnet is alternately energized and de-energized, displacing an armature back and forth between each end of a stroke. At one end the armature seals an air-supply line and at the other end a vacuumizing line. The lines are accordingly alternately connected to a valve chamber. The valve chamber communicates with the main valve through a control channel. The armature is connected to a diaphragm such as to provide axial guidance for the armature without friction.
A valve of this type is known for example from U.S. Pat. No. 4,196,751. The diaphragm in this valve is on the end of the armature opposite the electromagnet. To ensure that the air-supply line can be sealed, the surface of the armature is provided with an appropriate seal. The diaphragm is also in the form of a spring that opposes the motion of the armature toward the air-supply line with considerable resistance. Powerful reversing forces are necessary to overcome this resistance.
A valve is known from German U 9 114 953.3 wherein the armature extends through a diaphragm on the end opposite the electromagnet. When the magnet is energized, the armature is attracted to it and maintained there by remanence. Powerful reversing forces are necessary to overcome the remanence. This valve is only intended to control the flow of a medium, and it is not appropriate for connecting a control channel alternately to an air-supply line and a vacuumizing line.